A growing body of evidence suggests that many human solid tumors contain a significant fraction of hypoxic cells which can directly affect a number of malignant phenotypes, including therapeutic resistance, sustained angiogenesis, evasion of programmed cell death, tissue invasion and metastasis, and self-sufficiency in growth signals. This scenario is supported by clinical studies that correlate hypoxia with poor prognosis in a number of solid tumor types. These hypoxia-dependent phenotypic alterations are believed to involve, in part, a set of diverse hypoxic stress genes whose expression is controlled by specific hypoxia-sensitive transcription factors. The proposed research is based on the findings that the metal transcription factor-1 (MTF-1) is activated by hypoxia and that tumor expansion in hypoxic mouse fibrosarcomas requires MTF-1 expression. Furthermore, hypoxia-activated MTF-1 contributes to the development of cisplatin resistance in vitro. This ubiquitous transcription factor controls a number of hypoxic stress genes that, if overexpressed, could contribute to the development of clinically important malignant phenotypes in tumors containing transiently hypoxic microregions. The first set of studies (Aim 1) proposed in this competitive renewal is designed to clearly define the mechanisms associated with MTF-1 activation by hypoxia, including analysis of potential signaling pathways, phosphorylation events, regulation of the redox state of the MTF- 1 DNA binding domain, and nuclear translocation. Aim 2 uses microarray technology to identify other hypoxic stress genes that are controlled by MTF-1 and involves transcriptional analysis of a selected number of these MTF-dependent genes. The studies in Aim 3, utilizing both tumor xenograft and in vitro models will address the functional significance of hypoxia-mediated activation of MTF-1 in malignant progression. An understanding of these mechanisms will aid in the development of novel prognostic and therapeutic modalities, including gene therapy approaches, for solid tumors containing significant regions of recurring or transient hypoxia.